There have been known various systems of formatting data record for an optical recording medium. Among these systems is, for example, a system as shown in FIG. 15 which is suited for a recording medium of a card type.
In the system as illustrated in FIG. 15, tracking lines 1 are provided on a data recording region and clock bits 2 and a data track 3 are disposed, at predetermined intervals, along the lines 1. These are arranged in three lines and these three lines are further juxtaposed so that a plurality of data tracks may be provided in the data recording region.
In this data record formatting system, the reading/writing of data is carried out in a manner as illustrated in FIG. 15 in which a reading/writing head produces light beams B1, B2 and B3 so as to correspond to the juxtaposed three lines. One of the light beams is used for tracing the tracking line, another is used for detecting the clock bits and the rest is used for reading, writing and focussing.
However, the data record formatting system as described above involves the following problems:
Since this record formatting system has such a configuration that the three lines comprising the tracking line 1, the clock bit line 2 and the data track 3 are juxtaposed in the data recording region, the data track should be provided for every three lines. This reduces the recording density. Moreover, since the data reading/writing should be carried out while tracing the three lines juxtaposedly and conjointly, the intervals between the lines should be large enough, e.g. 10 .mu.m or more, so as to improve the accuracy of data reading/writing. This is especially crucial in the case of a card type recording medium, which has a relatively small data recording region, because the increased intervals between the lines lower the data recording capacity.